Centrifugal compressor.



S. A. MOSS.

CENTRIFUGAL COMPRESSOR.

APPLICATION FILED MAR, 12, I915.

Patented 001- 12, 1915;

Inventor; nFol-ci 1 1.. oss,

Witnesses UNITED STATES PATENT OFFICE.

SANFORD A. MOSS, OF LYNN, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

CENTRIFUGAL comrmisson.

' Specification of Letters Patent.

' Patented Oct. 12, 1915.

Application filed March 12, 1915. Serial No. 13,915.'

gal compressors, and particularly to the op-- cration of two or moresuch machines in parallel.

The invention relates more particularly to centrifugal compressors forcompressing air and will be described as applied to such use, but itwill be understood that it is not neces-. sarily limited thereto.

When two or more centrifugal compressors are connected to operate inparallel discharging into a common blast main the load will be. fairlyevenly distributed so long as the total load is such that that on eachmachine is of substantial value. This value varies with differentinstallations depending upon the characteristics of the particularmachines. When the total load falls. below this value there is atendency for one machine after another to drop its load to the remainingmachines which will eventually take all the load and drive air backthrough the other or others. This has led to considerable difficulty inoperating several machines in parallel. I V

'The ob]ect of the present inventionis to provide an improvedarrangement which will permit of two or more centrifugal compressorsbeing successfully operated in parallel at varying loads. i

In carrying out my invention Iprovide an automatically closing valve ordamper upon either the inlet side or the discharge side of eachcompressor, or all but one of them, and so arrange it that when airtends to pass through the machine in the reverse direction, it willautomatically close. By this arrangement whenever a' machine loses itsload, the passage through it will be automatically closed and hence theother machine or machines cannot force air through it backward. I

The accompanying drawing illustrates one form which my invention maytake and is the form which I now believe to be pref "erable.

7 Referring to the drawings, 1, 2 and 3 are three centrifugalcompressors connected to discharge into the common blast main 4. Thesecompressors may be of any suitable constructlon, and are of the type inwhich the delivery pressure varies with the load,

the pr ssure increasing with the load up to a certa 11 point and thendecreasing again with further increases in load. Arranged 1n the inlet 6of the compressor 1 is a gate valve or damper 7 having an operatinghandle 8 by means of which it can be moved and fastened in open, closed,or any intermedlate position. In the inlet 10 of each of the othercompressors is an automatic gate valve or damper 11 pivoted at 12.

This pivot is located to one side of the cen-' ter of the inlet andfixed to it is a' threaded rod 13 upon which is the adjustablecounterbalance weight 14. The weight is so adjusted that it at all timesbiases the valve slightly toward closed position. The pivot pin 12 isoffset to such an extent that when the valve is open it will stand a fewdegrees off center toward the closed position. 15 is a pin for pinningthe valve in closed position. The valve of compressor 2 is shown closed,but with the pin 15 screwed out so that it may open, and the valve ofcompressor 3 is shown pinned closed. The positions which the valve andcounterweight assume when the valve is in open position is shown indotted lines in connection with compressor 2.

The operation of my invention depends on the fact that asthe load on a.machine of this type, that is the number of cubic pressure produced byit varies. For no load, the pressure is a certain amount. As

the load increases the pressure increases somewhat up to a certain pointand then decreases again. At full load the pressure vmay be about thesame as at no load, and

at over load the pressure will still further decrease.

In operation the machines are all started and brought up to speed withthe valves closed, those of compressors 2 and 3 being pinned closed bythe pins 15. The valve 7 of compressor 1 is then gradually opened byhand. If the load on the entire system is less than a certainpredetermined minimum, for example, about one-third load for onemachine, pulsations will occur if the valve 7 is opened .Wide, so itmust be set at no i some intermediate point so as to eliminatepulsations. Under these conditions there is, of course, no need forother machines and they can then be shut down. .If, however, the valve 7can be opened wide without pulsations occurring, it shows that the loadmore than say the one-third value for onemachine. The valve? is thenlocked in the wide open position and the stop pins 15 of compressors 2and 3 are unscrewed so that the check .valves are free to open. If theload on the entire system is less than the to keep the check valves ofthe other compressors closed. If the load on compressor 1 now increaseswhen it reaches about full load, the pressure in the discharge pipe willbe about the no load pressure of machines 2 and 3. If it still continuesto increase, the pressure in the discharge pipe will become less thanthe no load pressure of the other machines. When this occurs the valve11 of one of these machines willopen. The Weights 14 of these twomachines will be so adjusted with regard to the characteristics of themachines that the valve 11 of one will open before the other. As soon asthe valve 11 of'the second machine opens,

say compressor 2, the load will then be divided between compressors 1and 2. This will mean that each of these machines is now carrying lessthan full load so that the discharge pressure increases and hence the vvalve 11 of machine 3 will remain closed. This state of affairs willcontinue until, as the load is increased, the pressure in the dischargepipe again drops to the no load pressure or slightly below. When thisoccurs, the valve 11 of machine 3 will automatically open and the loadwill then be divided among the three machines.

If now, with all three machines running with the load distributed amongthem, decrease in the load occurs, as soon as the load on each machinereaches a value where with further decrease a decrease in pressureoccurs an unstable condition will be .set up which causes oscillationsof the valves 11,

- which as already stated, are nearly balanced.

As soon as one of the check valves reaches a nearly closed position, inthis case it maintains a value greater than the ,maximum load pressureand hence greater than the no load pressure. This will then cause thevalve 11 to be closed. As soon as this occurs theload will then beautomatically distributed between two of the machines.

Should still further decreases in load occur the samecondltions willarise and theother automatic gate valve will close.

By the above structure it will be seen that nection with three machinesconnected in parallel but it will of course be understood that it may becarried out in connection with two machines or any number greater thantwo. p

In accordance with the provisions of the patent statutes, vI havedescribed. the principle of operation of my invention, together with theapparatus which'I now consider to represent the best embodiment thereof;but I desire to have it understood that the apparatus shown is onlyillustrative, andthat the invention can be carried out by other means. Ia

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The combination with a plurality of centrifugal compressors havinginlet conduits, and having discharge conduits which are connected inparallel to discharge into a common blast main, of valve means arrangedin the conduits of some of saidmachines which automatically close incase there is a tendency to force fluid backward through said machine ormachines.

2. The combination with a plurality of centrifugal compressors havinginlet con-, duits, and having discharge conduits which are connected inparallel to discharge into a common blast main, of an automatic valvebiased to closed position arranged in the inlet of one or more of saidmachines.

3. The combination with a plurality of centrifugal compressors havinginlet conduits, and having discharge'conduits which are connected inparallel to dischargeinto a common blast main, of a manually controlledvalve in the inlet of one. of said machines. andan automatic valve whichopens inwardly and is biased toward closed position in the inlet of eachof the remaining machines. 7 l

4. The combination withcentrifugal compressors having inlet conduits,and having dischargeconduits which are connected in parallel todischarge into a common blast main, of a manually cona plurality oftrolled valve in the inlet of one of said machines, an automatic valvewhich opensinwardly and is biasedtoward closed position in the inlet ofeach of the remaining machines, and means for fastening said last namedvalve or valves m closed posltion.

5. The combination with a plurality of centrifugal compressors havinginlet conduits, and having discharge conduits which are connected inparallel to discharge into a common blast main, of automatic valve meansarranged in the inlet of one or more of said machines, and adjustablemeans for biasing each valve to closed position.

6. The combination with a plurality of centrifugal compressors havinginlet conduits, and having discharge conduits which are connected inparallel to discharge into a common blast main, of a manually controlledvalve in the inlet of one of said machines, and an inwardly openingvalve in each of the others, said last named valve closed position, andmeans for fastening it closed.

7. The combination with a blast main, of

connected in parallel to said blast main, and

automatic valves .in the conduits of the last named compressors whichclose in case there is a tendency to force fluid backward therethrough.

In witness whereof, I have hereunto set my hand this eighth day of March1915.

SANFORD A. MOSS.

